This invention relates to a method of and an apparatus for removing residues particularly for the purpose of decontaminating nuclear installations and vessels.
A mechanical removal of residues from the surfaces of vessels and pipe conduits involves significant problems. The result of conventional processes is a loosening of the material rather than a removal thereof from the surface. The crusts are wedged on the surface and thus, although loose, they are not ready to drop off the vessel or pipe surface.
To effect an actual complete separation of the residues from the surface to be cleaned, German Patent No. 3,447,827 discloses a method and an apparatus which can be used similarly to pipe-cleaning hoses having a nozzle head. Other tools such as a steel brush may be moved laterally at the nozzle head in a longitudinal direction by intermittently applying fluid to a hydraulic cylinder. Other tools, for example, a hammer or hammers may be used with such an apparatus. It is a disadvantage of this arrangement that the residues and deposits are removed in an irregular manner and further, the apparatus may not treat locations which are not readily accessible.
Nuclear and chemical installations and reservoirs are often highly contaminated by sedimented residues. For a decontamination of such residues it is known to use chemical solvents. It is a disadvantage of such processes that a full decontamination by the permissible solvents cannot be effected.
Further, the use of supersonic devices for removing residues is also known. Thus, for avoiding damages during removal of deposits on fuel elements by means of ultrasonic waves, according to German Patent No. 3,238,886 the fuel elements are exposed simultaneously from opposite sides to ultrasonic waves of identical power. Such an arrangement, however, cannot be used in nuclear installations. It is a further disadvantage of such ultrasonic devices that high energy losses occur while the effective working radius is small.
According to a further well known process sandblasting is used for decontaminating nuclear installations. It is a drawback of sandblasting that secondary waste is generated. Thus, for example, the sand settles and also has to be removed which requires an additional energy input.